1. Field of the Invention
The present invention relates to threading devices generally and, more particularly, to an automatic threading device which may be temporarily or semi-permanently mounted on a turret or engine lathe and which can accommodate a wide range of threading functions with only relatively minor changes.
2. Background Art
There are a number of devices for forming threads on parts, whether the treads be external or internal, each method having its advantages according to the final product. Well known are the common manual taps and dies, each diameter and/or pitch of thread requiring its own tap and/or die. Threads may also be formed by stamping or casting. Thread rolling with flat or cylindrical dies is extensively used for mass production of screws and bolts. Thread milling is used in many instances, but the method requires expensive equipment.
The ordinary lathe can be used to accomplish almost any threading job by combining the rotation of the lathe with the synchronized feeding of a single pointed tool, generating the thread with no limitation of pitches, diameters, inside or outside, cylindrical or taper, and in any form of the thread itself. This method is slow and is typically used to manufacture replacement parts or a limited quantity of parts.
Automatic or semi-automatic production machines may be found in manufacturing operations, which machines are dedicated to producing threaded parts and are usually set up to produce a single threaded part for a relatively long production run and then may be modified to produce another threaded part. These machines offer the advantages of lathe threading methods with high speed and automatic cycling. The machines are very efficient, but come at a very high price not affordable to small and medium size operations.
Parts with threads against a flange or shoulder cannot be made with dies. Long shafts with two or more threads of different diameters and/or pitches are difficult, usually impossible, to produce with dies.
In my U.S. Pat. No. 3,016,777, issued Jan. 16, 1962, I describe a threading device for temporary attachment to a lathe, which device is semi-automatic in that it automatically moves a cutting tool back and forth parallel to the longitudinal axis of a part being threaded, but transverse advancement of the tool into the part is manual. In my Italian Patents Nos. 532273, issued Aug. 18, 1955, and 535380, issued Nov. 10, 1955, I describe improvements to that device wherein transverse feed is also automatic. While those patented devices have proved to be extraordinarily effective in providing a threading device which uses the mechanisms of the lathe itself to provide a wide range of types of threads. Such devices operate with a variety of gears, cams, ratchets, springs, and levers which contribute to slowness and which take a great deal of power to operate. Those devices are also relatively large and expensive and have a relatively low capacity.
Accordingly, it is a principal object of the present invention to provide a threading device for temporary or semi-permanent attachment to a lathe, which device can produce threads having a wide range of diameter, pitches, and lengths.
Another object of the invention is to provide such a device that is relatively compact and less expensive.
An additional object of the invention is to provide such a device that can be quickly mounted in position on the lathe.
A further object of the invention is to provide such a device in which changeover from one thread diameter, pitch, and/or length can be made quickly and easily.
Other objects of the invention, as well as particular advantages and features thereof will, in part, be obvious and will, in part, be apparent from the following description and the accompanying drawing figures.